1. Field of the Invention
The present invention relates to a conductivity measuring apparatus and a conductivity measuring method of measuring a conductivity of a sample of a board or the like, or a conductivity of a small sample.
2. Description of the Related Art
In order to measure an electric property of an extremely small region at a surface of a semiconductor or the like, as shown by, for example, Patent References 1, 2, there is used a conductivity measuring apparatus of a scanning tunnel microscope or the like having a measuring probe arranged with four styluses on straight lines at equal intervals. According to a conductivity measuring method by the measuring probe, a voltage is applied in a state of bringing two pieces of styluses arranged on an outer side (outer side probe) into contact with or proximate to a sample, a voltage drop generated by an electric resistance of the sample is measured by remaining two pieces of styluses arranged on an inner side (observing probe and grabbing probe), thereby, a surface property including section information at the position is measured.
According to the measuring probe, when the voltage is applied between the two outer side pieces of styluses, the more separated the interval between the two outer side pieces of styluses, up to the deeper position of the sample, the section information can be measured by the two inner side pieces of styluses.    Patent Reference 1: JP-A-2004-93352    Patent Reference 2: JP-A-2002-31655
However, according to the conductivity measuring apparatus of the background art, the following problem is posed.
First, two pieces of styluses arranged on the inner side are driven by drive sources separate from each other, and therefore, a separating distance of the two probes arranged on the inner side cannot accurately and continuously be adjusted.
Second, in relation to the first problem, the separating distance of two pieces of the styluses arranged on the inner side cannot accurately be adjusted, and therefore, there poses a problem that a conductivity of extremely proximate portions cannot accurately be measured.
Third, a force of pressing the measuring probe to the sample cannot be adjusted, and therefore, a reproducibility of the pressing force is poor.
Fourth, two pieces of the styluses arranged on the inner side are driven by the drive sources separate from each other, and therefore, the electric property cannot be measured by accurately picking up a small sample.
Fifth, a conductivity of a predetermined portion cannot be measured by selecting and grasping the predetermined portion by observing a shape of the sample and by being isolated from the other portion.